In recent years, with the advancements in speed-up and energy conservation of the machines, toners having excellent low-temperature fixing ability are in demand. As resin binders for toners, numerous polyesters having excellent low-temperature fixing ability are being studied, among which a polyester obtained by using, as a raw material monomer, a carboxylic acid having an aromatic ring capable of improving a glass transition temperature while maintaining a low softening point is being used.
Patent Publication 1 discloses, as an objective of providing a toner for electrostatic image development having a smaller amount of smaller size fine particles which are formed as a by-product during the polymerization of a toner, and further having a reduced residual amount of a degradation product of a polymerization initiator remaining in the toner, a method for producing a toner for electrostatic image development, including the steps of suspending a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in an aqueous dispersion medium containing a dispersion stabilizer to provide a suspension dispersed with liquid droplets of the above-mentioned polymerizable monomer composition; and polymerizing the polymerizable monomers in the above suspension including subjecting the polymerizable monomers to a suspension polymerization in the presence of a polymerization initiator, to provide colored resin particles, wherein in the suspending step for providing the above suspension, an inhibitor for forming smaller size fine particles is contained in an aqueous dispersion medium in an amount of from 0.01 to 1 part by weight, based on 100 parts by weight of the polymerizable monomer, and the publication describes caffeic acid as an inhibitor for forming smaller size fine particles.
Patent Publication 2 discloses, as an objective of providing a method of deinking and regenerating an image-receiving sheet used in a method for forming fixed images according to electrophotography or the like, a microencapsulated toner characterized in that the microencapsulated toner comprises a core material having a colorant which is reversibly capable of developing color and removing color, and a shell material made of a shell forming resin for coating the core substance, and the publication describes coumaric acid as a colorant.